Browsing by Author "Tsai, KC"

Now showing 1 - 9 of 9

Alkylation of nanoporous silica thin films by high density plasma chemical vapor deposition of a-SIC : H
(2004-05-01)
Pan, FM
;
Wu, BW
;
Cho, AT
;
Tsai, KC
;
Tsai, TG
Film stacks of a-SiC:H and molecularly templated nanoporous silica thin films have been prepared, and alkylation of pore surfaces of the nanoporous silica layer by the a-SiC:H layer was studied. The a-SiC:H thin films were deposited by high-density plasma chemical vapor deposition (HDP-CVD) using trimethylsilane (3MS) as the precursor. Carbon is found to uniformly distribute in the thin nanoporous silica film, and the carbon content in the nanoporous film decreases with increasing the a-SiC:H deposition temperature. We used the modified Sanderson formalism to estimate the corresponding Si(2p) and C(1s) electron energies in x-ray photoelectron spectra (XPS) for possible terminal species on pore surfaces in the nanoporous silica layer. According to the XPS analysis and thermal desorption mass spectroscopy, the terminal species are probably in the chemical form of alkoxyl structures. The alkoxyl terminal groups introduced into the nanoporous silica thin film are believed to stem from hydrocarbons trapped in microvoids in the a-SiC:H film, which are formed during the HDP-CVD deposition. The terminal alkoxyl groups in the nanoporous silica layer can greatly enhance the hydrophobicity of the nanoporous silica dielectric, and hence improve the dielectric property of the film stack of a-SiC:H/nanoporous silica. An effective dielectric constant smaller than 1.7 can be obtained for the film stacks. (C) 2004 American Vacuum Society.
Axial load behavior of stiffened concrete-filled steel columns
(2002-09-01)
Huang, CS
;
Yeh, YK
;
Liu, GY
;
Hu, HT
;
Tsai, KC
This study investigates the axial load behavior of concrete-filled steel tubular (CFT) columns with the width-to-thickness ratios between 40 and 150, and proposes an effective stiffening scheme to improve the mechanical properties of square cross-sectional CFT columns. Seventeen specimens were tested to examine the effects of cross-sectional shapes, width-to-thickness ratios, and stiffening arrangements on the ultimate strength, stiffness, and ductility of CFT columns. Moreover, nonlinear finite element analysis was also conducted to investigate cross-sectional axial stress distribution at the ultimate strength. Comparing the measured ultimate strength with estimates by using some current specifications suggested that current specifications may considerably underestimate the ultimate strength of circular CFT columns, particularly for columns with a small width-to-thickness ratio. Results in this study demonstrate that the proposed stiffening scheme can significantly enhance the ultimate strength and ductility of square CFT columns.
Characteristics of fluorinated amorphous carbon films and implementation of 0.15 mu m Cu/a-C : F damascene interconnection
(2001-05-01)
Shieh, JM
;
Suen, SC
;
Tsai, KC
;
Dai, BT
;
Wu, YC
Fluorinated amorphous carbon films (a-C:F) deposited by plasma enhanced chemical vapor deposition with low dielectric constant (K similar to2.3), thermal stability (higher than 400 degreesC) and acceptable adhesion to a cap layer such as SiOF or SiO2 were obtained by varying the range of content ratios between carbon and fluorine, the rf power, the process pressure and the base temperature. Standard x-ray photoelectron spectroscopy and thermal desorption spectroscopy metrologies were employed to characterize the deposited a-C:F films. The damascene pattern with 0.15 mum and an etching selectivity of more than 50 (a-C:F/SiOF, SiO2) was implemented by a mixture of etching gases of N-2+O-2. The bias power, rf power and gas hows were incorporated to optimize the etching recipe for achieving a damascene profile with a high aspect ratio. The scanning electron microscope results showed that a better etch profile can be obtained at higher bias power. In our damascene architecture, the etching stop layer or hard mask of both SiOF and SiO2 was studied. The SiOF, providing a lower dielectric constant than SiO2, would especially reduce the entire effective dielectric constant. Furthermore, we integrated electroplated copper into trenches or vias as small as 0.15 mum, with aspect ratio of 6. (C) 2001 American Vacuum Society.
High-reliability Ta2O5 metal-insulator-metal capacitors with Cu-based electrodes
(2006)
Tsai, KC
;
Wu, WF
;
Chao, CG
;
Kuan, CP
;
材料科學與工程學系
The properties of tantalum oxide (Ta2O5) metal-insulator-metal (MIM) capacitors with Al/Ta/Cu/Ta bottom electrodes were investigated. An ultrathin Al film successfully suppresses oxygen diffusion in the Ta2O5 MIM capacitor with the Cu-based electrode. The electrical characteristics and reliability of Ta2O5 MIM capacitors are improved by addition of ultrathin Al films. Ta2O5 MIM capacitors have low leakage current density (1 nA/cm(2) at 1 MV/cm) and high breakdown field (5.2 MV/cm at 10(-6) A/cm(2)). The decrease in leakage current is attributed to the formation of a dense and uniform Al2O3 layer, which has self-protection property and stops further oxygen diffusion into the tantalum contact. The dominant conduction mechanism of leakage current is the Poole-Frenkel effect at electric fields above 1.5 MV/cm. (c) 2006 The Electrochemical Society.
Influence of N2O plasma treatment on microstructure and thermal stability of WNx barriers for Cu interconnection
(2004-05-01)
Tsai, KC
;
Wu, WF
;
Chen, JC
;
Pan, TJ
;
Chao, CG
Thermal stabilities of Cu-contacted n(+)-p junctions with tungsten nitride (WNx) diffusion barriers deposited at various nitrogen flow ratios are investigated. N2O plasma treatment is applied to improve thermal stability and barrier performance of WNx film. Sheet resistance Of Cu/N2O plasma-treated WNx/Si is fairly stable even after annealing at 750degreesC for 30 min. Moreover, N2O plasma treatment enables the Cu/WNx/n(+)-p junction-diodes to sustain thermal annealing at 600 degreesC without electrical degradation. Auger electron spectroscopy depth profiles show that Cu diffusion through the N2O plasma-treated WNx barrier is extremely limited, even after annealing at 675 degreesC. Analyses of transmission electron microscopy and x-ray photoemission spectroscopy show that nitridation and oxidation on the WNx barrier occur and an amorphous layer is formed after N2O plasma treatment. (C) 2004 American Vacuum Society.
MR-FQ: A fair scheduling algorithm for wireless networks with variable transmission rates
(2005-01-01)
Wang, YC
;
Tseng, YC
;
Chen, WT
;
Tsai, KC
;
資訊工程學系
Wireless networks are characterized by bursty and location-dependent errors. Although many fair scheduling methods have been proposed to address these issues, most of them assume a simple two-state channel model, where a channel can be either good or bad. However, the situation is not so pessimistic since different modulation techniques can be adapted to different channel conditions. Multi-rate transmission is a common technique for wireless networks nowadays. This leads to a dilemma: should fairness be built based on the amount of medium time that a user utilizes or the amount of services that a user receives? In this work, we propose a Multi-rate wireless Fair Queueing (MR-FQ) algorithm that allows a flow to transmit at different rates according to its channel condition and lagging degree. MR-FQ takes both time and service fairness into account. It not only guarantees fairness and bounded delays for packet flows, but also increases the overall system throughput.
Novel multilayered Ti/TiN diffusion barrier for Al metallization
(2005-08-01)
Wu, WF
;
Tsai, KC
;
Chao, CG
;
Chen, JC
;
Ou, KL
A novel, multilayered Ti/TiN diffusion barrier is proposed and successfully applied for Al metallization. The multilayered Ti/TiN structure is effective in enhancing the barrier properties since the very thin Ti layer inserted into titanium nitride (TiN) barrier can cause disruption of the TiN columnar growth and reduction of open grain boundaries resulting in retarded interdiffusion between metal and silicon. Multilayered Ti/TiN films are deposited sequentially by sputtering without breaking vacuum. It is found that TiN grain boundaries are discontinuous when a Ti layer is inserted into TiN. Multilayered Ti/TiN has a better barrier performance than single-layer TiN in Al metallization. However, the barrier performance is related to the number and thickness of the inserted Ti layers, because increasing titanium will enhance chemical reactions between Al and barrier layers, and produce more titanium-aluminum compounds. The total thickness of introduced Ti layers should be reduced to improve barrier performance.
Numerical and experimental analysis of Cu diffusion in plasma-treated tungsten barrier
(2005)
Tsai, KC
;
Wu, WF
;
Chen, JC
;
Pan, TJ
;
Chao, CG
This work investigates Cu diffusion in sputtered and N2O plasma-treated W films. N2O plasma-treated W barrier has a nanostructured surface layer and shows high thermal stability and the best barrier properties. Also investigated herein are the lattice and grain boundary diffusivities extracted from the Cu penetration depth profiles using the Whipple analysis of grain boundary diffusion and Fick's second law of diffusion. Analysis indicates that the diffusion models correlate well with experimental results. (C) 2004 The Electrochemical Society.
Reduction of etching plasma damage on low dielectric constant fluorinated amorphous carbon films by multiple H-2 plasma treatment
(2002-07-01)
Shieh, JM
;
Tsai, KC
;
Dai, BT
;
Wu, YC
;
Wu, YH
Two-step hydrogen plasma treatment on low dielectric constant (low-k) fluorinated amorphous carbon films (a-C:F) was conducted to improve their thermal stability and reduce the damage caused by the patterning processes. First, hydrogen plasma treatment repairs imperfect bonds of as-deposited a-C:F films, stabilizing their chemical structures and increasing their resistance against elevated thermal stresses. After this passivation process, an additional hydrogen plasma treatment was applied to a-C:F films that had been etched using a mixture of N-2+O-2+CHF3, enabling sub-130 nm damascene trenches to be patterned and repairing the chemical structures destroyed by the etching plasma. (C) 2002 American Vacuum Society.